1. Field of the Invention
The present invention relates to an abrasive article comprising a binder, abrasive grains, and an antiloading component.
2. Discussion of Related Art
There are numerous types of abrasive articles. For example, an abrasive article generally comprises abrasive particles bonded together as a bonded abrasive article, bonded to a backing as a coated abrasive article, or bonded into and/or onto a three-dimensional nonwoven substrate as a nonwoven abrasive article. Each type of abrasive article may also be in a variety of forms. For example, a coated abrasive article can comprise a first layer (also known as a make coat), a plurality of abrasive particles adhered thereto and therein, and a second layer (also known as a size coat). In some instances, a third layer (also known as a supersize coat) may be applied over the size coat. Alternatively, a coated abrasive article may be a lapping coated abrasive comprising an abrasive coating (which also can be referred to as an "abrasive layer") bonded to a backing where the abrasive coating comprises a plurality of abrasive particles dispersed in a binder. In addition, a coated abrasive article may be a structured abrasive comprising a plurality of precisely shaped abrasive composites bonded to a backing. In this instance, the abrasive composites comprise a plurality of abrasive particles.
Abrasives articles are used to abrade a wide variety of substrates or workpieces made from, for example, wood, plastic, fiberglass, or soft metal alloys, or having a layer of enamel or paint. Typically, there is some degree of space between these abrasive particles. During the abrading process, material abraded from the substrate or workpiece, also known as swarf, tends to fill the spaces between abrasive particles. The filling of spaces between abrasive particles with swarf and the subsequent build-up of swarf is known as loading. Loading presents a concern because the life of the abrasive article is reduced and the cut rate of the abrasive article decreases (thus, more force may be required to abrade). In addition, loading is an exponential problem; once swarf begins to fill in the spaces between abrasive particles, the initial swarf acts as a "seed" or "nucleus" for additional loading.
The abrasive industry has sought loading-resistant materials to use in as abrasive articles. Examples of loading-resistant materials which have been used include metal salts of fatty acids, urea-formaldehyde resins, waxes, mineral oils, crosslinked silanes, crosslinked silicones, and fluorochemicals. Preferred materials have been zinc stearate and calcium stearate. One theory for the success of metal stearates as an antiloading agent is that the metal stearate coating powders off the coated abrasive surface during the abrading process, which in turn causes the swarf to also powder off of the surface, thus reducing the amount of loading.
Stearate coatings for the prevention of loading have been utilized by the abrasives industry for several decades. It has been common to utilize a binder with the stearate to assist in applying and retaining the coating on the abrasive surface. Some minor improvements over the years have been made by utilizing stearates with higher melting points, for example, calcium or lithium stearate and by incorporating additives to enhance antiloading performance, for example, fluorochemicals.
Specific attempts to solve the problem of loading include those taught in U.S. Pat. Nos. 2,768,886 (Twombly); 2,893,854 (Rinker et al.); and 3,619,150 (Rinker et al.). U.S. Pat. No. 2,768,886 discloses an abrasive article with a coating of small, solid particles consisting essentially of stearates or palmitates. U.S. Pat. No. 2,893,854 discloses a coated abrasive article coated with a continuous film of a resin having uniformly dispersed small, solid particles of a water-insoluble metallic soap of a saturated fatty acid having from 16 to 18 carbon atoms. U.S. Pat. No. 3,619,150 discloses a coated abrasive article having a nonloading coating comprising a mixed resin composition of a thermosetting resin and either a thermoplastic or elastomeric resin and a water-dispersible metallic soap, in particular, a metallic water-insoluble soap of a C16 to C18 saturated fatty acid, dispersed throughout the resin composition.
U.S. Pat. No. 4,609,380 (Barnett) discloses an abrasive wheel having a binder system comprising a binder and a smear-reducing compatible polymer and conventional lubricants including metal stearate salts such as lithium stearate.
U.S. Pat. No. 4,784,671 (Elbel) discloses a process for improving the grinding performance of a porous ceramic or plastic bound grinding or honing body comprising filling the pore spaces at least in part with at least one metal soap, including salts and soaps of the fatty acids of lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid. A grinding performance improvement disclosed is reduction of clogged pores of the body to avoid rewelding and sheet metal jacket formations.
U.S. Pat. No. 4,988,554 (Peterson et al.) discloses a coated abrasive article having a backing having a layer of abrasive grains overcoated with a loading resistant coating comprising a lithium salt of a fatty acid on one side and a pressure-sensitive adhesive on the other side of the backing.
U.S. Pat. No. 4,396,403 (Ibrahim) discloses a coated abrasive article, which does not need a supersize coat of metal stearates or any other material, which instead incorporates phosphoric acids, partial esters of such acids, amine salts of such acids and partial esters, and/or quaternary ammonium salts with at least one long substituent group into amino resin or glue sizing adhesives during the manufacture of the coated abrasive article.
U.S. Pat. No. 4,973,338 (Gaeta et al.) discloses a coated abrasive that has been oversized with an antiloading amount of a quaternary ammonium anti-static compound comprising from about 15 to 35 carbon atoms and having a molecular weight not less than about 300. Examples of the quaternary ammonium compounds include (3-lauramido-propyl)trimethylammonium methyl sulfate, stearamidopropyldimethyl-beta-hydroxyethylammoniumnitrate, N,N-bis(2-hydroxyethyl)-N-(3'-dodecyloxy-2'-hydroxypropyl)methylammonium methosulfate and stearamidopropyl-dimethyl-beta-hydroxyethylammoniumdihydrogen phosphate. Typically, the quaternary ammonium compound is coated out of a solvent, typically an aqueous alcohol solvent system.
U.S. Pat. No. 5,164,265 (Stubbs) discloses an abrasive article having, either applied as a layer coated over existing layers of an abrasive article or incorporated into the coating formulation which will form the outermost layer of the binder, a fluorochemical compound selected from the group consisting of compounds comprising a fluorinated aliphatic group attached to a polar group or moiety and compounds having a molecular weight of at least about 750 and comprising a non-fluorinated polymeric backbone having a plurality of pendant fluorinated aliphatic groups comprising the higher of (a) a minimum of three C--F bonds, or (b) in which 25% of the C--H bonds have been replaced by C--F bonds such that the fluorochemical compounds comprises at least 15% by weight of fluorine.
Although the abrasive industry has widely used metal stearates with a good degree of success, the industry is always looking for improved antiloading components, particularly to lengthen product life. Although there have been a number of improvements recently for backings, bond systems, and minerals of coated abrasives, comparable improvements in antiloading components have not yet been achieved. That is, the industry is still seeking a component which is easy to apply, is relatively inexpensive, and can be utilized during abrading of a variety of workpieces including paint, wood, wood sealers, plastic, fiberglass, composite material, and automotive body fillers and putties.